The on resistance (RDSON) of a p-channel device is inversely proportional to gate drive voltage. FIG. 1 is a graph illustrating this inverse relationship. Thus, p-channel devices have high RDSON when operating in low voltage conditions in which gate voltage is not fully driven. Higher RDSON creates higher power dissipation, which is undesirable.
Due to conflicting trade-offs, it is difficult to select an appropriate p-channel device for a system. Selecting a high voltage p-channel device for low voltage operation where gate drive is not optimal results in high RDSON. Selecting a low voltage p-channel device can improve the RDSON but results in higher channel and junction leakage. Junction voltage breaks during high voltage operation if the voltage rating of the p-channel is exceeded. Thus, selecting a low voltage p-channel device significantly limits range of operation. Selecting a p-channel device with a larger p-channel area may achieve a desired RDSON but at the expense of a larger footprint.
A p-channel device is typically best suited for a system in which the supply voltage range can be restricted. In such cases, an optimal p-channel operation voltage can be selected for that supply voltage range. It would be useful for p-channel devices to be suitable for a wider class of systems.